Historically, the red spruce (picea rubens) has been an important timber species in the United States. However, many natural and human actions have led to its decline. Not only has acid rain and land use changes resulted in the loss of many red spruce trees, but damaging winters also play a role in limiting tree growth as heavy snow can break branches.

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In the course of studying the lingering effects of acid rain and whether trees stored less carbon as a result of winter injury, U.S. Forest Service and University of Vermont scientists came up with a surprising result for the species' decline.

Paul Schaberg, a research plant physiologist with the U.S. Forest Service's Northern Research Station, and partners studied red spruce trees in Vermont, New Hampshire and Massachusetts. They found that the influence of a single damaging winter injury event in 2003 continued to slow tree growth in New England for 3 years which is longer than had been expected. Scientists also discovered that this had a significant impact on carbon storage where the cumulative reductions were equivalent to the carbon produced by burning 280 million gallons of gasoline.

They also found something they did not expect.

"The shocking thing is that these trees are doing remarkably well now," said Schaberg. Researchers found that diameter growth is now the highest ever recorded for red spruce, indicating that it is now growing at levels almost two times the average for the last 100 years. But why?

The theories include whether the red spruce turn-around can be credited to reductions in pollution made possible by the Clean Air Act of 1990, which helped reduce sulfur and nitrogen pollution. Another possibility is that red spruce may be one of nature's winners in the face of climate change as warmer winters mean less damage to foliage, which limits growth for the red spruce. Questions for future research also include whether the historic growth rate will continue or whether it will plateau.

Michael T. Rains, Director of the Northern Research Station and the Forest Product Laboratory stated: "Whether this is a success story for pollution control or a developing story about the effects of a changing climate, we are not yet sure."

The study, "Quantifying the legacy of foliar winter injury on woody aboveground carbon sequestration of red spruce trees," was published earlier this year in the journal Forest Ecology and Management.